Electrical fine tuning device



Feb. i0, 1959 M. G. GossARD 2,873,374

, ELECTRICAL EINE TUNING DEVICE Filed May 27, 1955" 4 sheets-sheet I Ma? /If im Arraewf Feb. l0, 1959 Filed May 2 M. G. GOSSARD ELECTRICALFINE TUNING DEVICE IIE- 157.

4 Sheets-Sheet 2 INVENTOR. M. 6L EAW Goss/:ea

United States Patent() ELECTRICAL FINE TUNING DEVICE Morris GlennGossard, Burbank, Calif., assignol' to Standard Coil Products Co. Inc.,Los Angeles, Calif., a corporation of Illinois Application May 27, 1955,Serial No. 511,642

4 Claims. (Cl. Z50-40) The present invention relates to electrical finetuning devices, and more particularly relates to a novel fine tuningmechanism for television tuners.

In prior tine tuning devices, particularly for the frequencies used intelevision reception, the effect of the tine tuning increments offrequency change diminished at one or the other end of the receptionband. Furthermore, the range of prior tine tuning devices did notelectively cover the entire reception band, as for example all thetwelve very high frequency (V. H. F.) channels. The television band forV. H. F. ranges from 54 to 88 megacycles, encompassing channels 2 to 6;and from 174 to 216 megacycles, encompassing channels 7 through 13. Thepresent invention is directed to novel tine tuning devices effectivethroughout such frequency range of 54 to 216 megacycles; and beyond,should such be desired.

In accordance with the present invention, an inductance section of thene tuning device is placed in circuit with the oscillator, and acapacitive element is also incorporated therewith. Novel means areprovided whereby both the inductance and the capacity in the fine tuningdevice are varied to directly aifect the frequency of the oscillator. Ithas been found that the devices of the present invention are effectivethroughout the twelve V. H. F. channels, at both ends thereof, and infact is linear in its operation of ne tuning a frequency shift withrespect to the operating drive and provides a full range of twomegacycles variation for all V. H. F. channels. The devices of thepresent invention are also usable as an oscillator trimmer, as will bemore fully set forth hereinafter.

1t is accordingly an object of the present invention to provide a noveltine tuning device effective over a wide frequency spectrum.

Another object of the present invention is to provide a novel tinetuning mechanism eiective throughout a wide frequency range incontrolling frequency shifts of an oscillator therewith.

A further object of the present invention' is to provide a novel netuning mechanism incorporating both inductance and capacitance, relatedto an oscillator circuit, and wherein the parameters of the mechanismare changed by mechanical displacement.

.Still another object of the present invention is to provide a novelfine tuning device incorporating an inductive element in circuit with anoscillator circuit, and a capacitance that is changed by mechanicaldisplacement, to eliect frequency shifts in the oscillator throughparameter changes in the inductance thereof.

Another object of the present invention is to provide a novel finetuning control that affords `a substantially linear line tuningfrequency change effect in an oscillator, over a wide frequency range ofoperation thereof, as related to mechanical displacements inthe linetuning control.

These and further objects of the present invention will ICC become moreapparent in the following description thereof, taken in connection withthe drawings in which:

Figure 1 is top view of an exemplary embodiment of the novel tine tuningdevice, in circuit connection with an oscillator.

Figure 2 is an end View of the tine tuning device of Figure 1.

Figure 3 is a schematic diagram of the oscillator circuit of Figure 1,incorporating the invention line tuner.

Figure 4 is a plan view of the inductance loop of the ne tuning deviceof Figure 1.

Figure 5 is a side elevation view of the inductance loop of Figure 4.

Figure 6 is a top view of the mounting base of the fine tuning device.

Figure 7 is a cross-sectional View through the base of Figure 6, takenalong the line 7--7 thereof.

Figure 8 is a top view of the blade element of the fine tuning device.

Figure 9 is a front elevational view of the blade of Figure 8.

Figure 10 is an end elevational view of the blade as seen from the rightside of Figure 9.

Figure 11 is an elevational view of a modified iine tuning device,partially broken away, and in circuit with an oscillator.

Figure 12 is a schematic electrical representation of the system ofFigure ll'.

Figure 13 is an end view of a further embodiment of a iine tuning devicein accordance with the present invention.

Figure 14 is a bottom view of a portion of the device of Figure 13 asseen at the arrows 14-14 thereof.

Figure 15 is an end elevational View of a television tuner incorporatingthe fine tuning device of Figure 13.

Figure 16 is a side elevational view of the tuner of Figure 15.

An exemplary form of the fine tuning device of the invention is shown incircuit with an oscillator in Figure 1. Fine tuning device 15 comprisesa base 16 and an inductance loop 17 mounted in a recess 18 within base16. A spring blade 20 is mounted on the top of base 16, and insulatingboard 21 is gripped to the top surface of blade 20 by lips 22, 22 on thesides thereof.

The flat loop 17 serves as an inductor in circuit with the oscillator25. Oscillator 25 comprises a triode electron tube 26, having plateelectrode 27 connected to one end 28 of loop 17. The opposite terminallug 29 of loop 17 is connected to inductance 3i) of oscillator 25, atterminal 31 thereof. Terminal 32 of inductance 30 is connected to gridelectrode 33 of triode 26 through condenser 34. A self-biasing resistor35 is connected between grid 33 and cathode 36, to ground. The plate orB-isupply for oscillator 25 is connected to anode 27 through inductance30 and loop 17, in series therewith through dropping resistor 37 betweenB+ and lead 3i; to terminal 32. A condenser 4G completes the oscillatorcircuit, connected between lead 3S and ground.

The fine tuning device l5 comprises essentially an inductorcorresponding to loop 17 mounted in an insulation base 16, andelectrically connected in the inductance circuit of oscillator 25between inductance 3i) and anode Z7. The blade 20 is supported aboveloop 17 in device 15 and is connected to ground through lead 41. Blade20 is accordingly capacitatively coupled to the iiat loop 1'7,constituting a capacitance between loop 17 and ground.

The elevational view, Figure 2 of tine device 15 illustrates the normalopen position of blade 20 above at inductance loop 17. Blade 20 is madepreferably of a spring material, such as Phosphor bronze, and has avertical projection e2 set into a groove in base 16. The extendedarrangement of blade 20 is in the upwardly biased position (Figure 2),spring-pressed against the full flat 46 in tine tuning shaft 45. Theopen position of blade Ztl in Figure 2, affords the minimum capacitativecoupling thereof with inductance loop 17.

The fine tuning shaft 45 extends across the surface of insulation board21. Tuning shaft 45 is mounted in suitable bearings (not shown), andcontains a v180" flat 46 as seen clearly in Figure 2. The relationshipof tuning shaft 45 to the line tuning device 15, in the exemplaryembodiment, is shown in dotted lines in Figure l. Shaft 45 is rotatablelin either direction as shown by the arrow u. Rotation of shaft d5causes abutment of the solid 180"V portion thereof against insulationplate 2l, moving Y it against the spring action Vof blade 2b.. Blade 20is thereupon pressed angularly closed to base 16, and accordingly to theflat loop 17 therein.

The up-and-down swing of blade 20 is illustrated by `the arrow b, inFigure 2. The electrical effect of the angular swing of blade 2li of theline tuning device 15, is described in more detail in connection withschematic Figure 3 hereinafter. Details of an exemplary construc-Y tionfor the inductance loop 17 are shown in Figures 4 andS. Further detailsof the mechanical construction of the hue tuning device as embodied inFigures l and 2, are described and illustrated in connection withFigures 6 through l0, hereinafter. It is to be understood that theangular swing of blade may be accomplished by suitable means other thanshaft 45.

Figure 3 is a schematic representation of the oscillator Y of Figure l,in conjunction with a diagrammatic representation of line tuning device15, indicated Vas 15a. The inductor loop 17 is represented by inductance17a, in the series between the anode 27 and inductancel). The planarembodiment of inductance 17 forms an effective condenser plate,indicated in dotted at 50 for induce ance 17a. The blade 20 in effectforms a condenser plate 20?' of a condenser yrelated to the eifectivecapacity plate 50 of inductor 17a. Condenser plate 20a is connected toground (Figure 3), corresponding to its circuit connection in Figure l.Y

Rotation of shaft 45 moves the condenser plateZila, corresponding toblade 20 of Figure 2, for a variable physical relationship and spacingwith respect to the effective condenser plate 50. The arrow b of Figure3 illustrates a relative movement of plate 20@ with respect to theeffectively iixed plate Sil. A definite capacity or condenser Copisformed by plates 20a and 50. ln Fig` ure 3 the effective condenser C0 isshown connected betweenV the inductance 17a (where it joins inductor30), and ground. Variation of the capacitance of C0 (24F- 50) creates' adenite change in the frequency at any given setting, with givenparameters of oscillator' 25, as will be understood by those skilled inthe art.

. Still another important electrical effect accrues from the inventionline tuning device. It has been found that by changing the position ofblade 29 with respect to inductor loop 17, an effective change occursalso in the inductance of loop 17. Such variation in the effectiveinductance 17a ofV schematic Figure 3, is indicated by variable LU. Itis thus now apparent that the line tuning device 15 of the inventioncomprises an inductance (17) connectable in circuit with an electronicoscillator (2,5), and contains a variable.l capacity element (CU) thatalso changes effectively the inductance (L0) of the device. Thecomposite ne tuning device 15 is simple, inexpensive and effectivethroughout the tuning range of, for example, a V. H. F. tuner. 1

It has been found that device 15 is operative such that for the lower V.H. F. channels (namely channels 2 to 6 with frequency range ofv 54 to 88megacycles), the change ofV capacitance CD lby relative spacings ofblade 20 top at inductor 1001317 is eiectiveto-shift thefrequency ofoscillator 25; while for the higher vchannels (namely in the 174 to 216megacycle range of channels 7 to 13), the capacity effect is lessimportant for the frequency shifts than the change of the inductance(L0) in the oscillator through the effective inductance 17a. Such actionin effect results in decreasing inductance L0 when the frequency of theoscillator V25 is in the higher range to Vcompensate or otherwisenegative the corresponding increase of capacitance Co, when blade 20approaches coil 17. Y

It is to be understood that Where the device 1S isV used in a televisiontuner, that the oscillator (25) is tuned to frequencies above (or below)the corresponding carrier frequencies of the channels to-aord a best frequency output as the intermediate frequency (I. F.) Vfor the receiver.It is also understood that the device 15 for line tuning oscillator 25raises (or lowers) the pretuned oscillator basis setting frequencythrough shaft l45 for the line resolution tuning of the receiver.

VVThe'net effect of the frequency change in oscillator 25 by suchcomposite action of C0 and L0 in device 15 is the same as toautomatically place smaller capacity changes for the higher frequencies.Otherwise a given capacity change in a'high frequency oscillator resultsin a greater shift orrchange of frequency in the oscillator, than thesame capacity change would produce in a lower frequency oscillator. Ithas been found that the device 1S ofthe'invention affords approximatelyequal displacements (shifts) of frequency throughout the twelve channelsfor given angular rotation of the drive l5 in a V. H. F. televisionreceiver. device 15 as a variable trimmer condenser C0 primarily in thelower band of the V. H. F. frequencies, and the reduction of the C9capacitance by a corresponding L0 decrease effective in the higherfrequencies of the V. H. F. band, provides the novel uniform frequencyshifting or ne .tuningfaction for reception of each channel.

It is to be understood that the device 15 ofthe invention is applicableto other frequency bands than V. H. F. channels in television. It isuseful also, for example, in frequency modulation broadcasting inultra-high frequency (U. H. F.) television broadcasting, and in otherforms and ranges of communication. The exemplary device is described forV. H. F. broadcasting for purposes of illustration.V

An exemplary flat loop construction corresponding to 17 of Figures. land 2is shown inFigures 4 and 5, beingV plan end and elevational viewsrespectively. The loop 17 is of metallic material, such as half-hardbrass, 26 gauge.

In a particular embodiment, the inside rectangular. dimendatand set intoarecess'in the base 16, and rigidly mount- V ed in the base through thelugs 54, 55, 56 integral therewith. Electrical connection to inductanceloop 17 is made through the end terminals 2S, 29 as aforesaid.`

The plastic base 16 for device 15 is detailed in ures 6 and'7.Y The topplan view of base 16 is shown with loop 17 recessed therein. Therecessed portion of the base; 16 corresponding to the'groove 57 in thetop ofthe base.' The material for base 16 may be a rncldable ma terialsuch asPlascon Alkaloid #430, polystyrene, Lu-` cite, or other suitablematerial of low dielectric constant. Base 16 contains the three notchesor slots di), el and 62 within which the depending lugsSd, 55, 56 ofloop 17 are set. The under portions of the notchestl, 61, 62, namely60', 61', andV 62, are undercutin order to receive the springprojections 54e, 55a, and 56a, and hold loop 17 fast'to base 16, inpredetermined recessV 5,7 v

thereoi'f The recess 42a at the left side of base 16, is for the Theeffective operation ofprojection 42 of blade 20, seen in Figure 2. Afurther cavity 6 5 having a recess 65a is seen in Figures 6 and 7. Thepurpose of the 'cavity-recess G5-65a is to receive a liook 70 (indicatedin Figure 2) that is punched out from the base 75 upon which the linetuning device is secured. The base 7Smay be the metallic chassis of thetuner or equipment with which the ne tuning device is connected. Theintegral projections k6 6 and 67 constitute the base feet of themounting base 16 of device 15. Tip 71 of hook 70 grips base 16 at therecess 65a thereof, through a sliding action, to mount device againstthe panel 75. Device 15 remains against panel 75, held in position in arelatively rigid relationship. In the exemf plary embodiment, theoverall dimensions of the base 16 were 1" long, 1/z wide, and about laoverall height.

The depth of loop recess 57 invbase 16 in the described embodiment was.03, corresponding to about twice the thickness of the loop 17. In thismanner 'electrical contact between loop 17 and the blade 20 co-actingtherewith is avoided in, all instances. The device 1.5 accordingly actswith only capacitive and inductive changes in the elements thereof underall operating conditions, withhout actual or sliding contacts.

Figures 8, 9 and 10 are exemplary illustrationsof springcapacitive blade20 of fine tunning device 15. The `blade 2,0 contains body S0, with adepending leg `42. The leg 42 is mounted within the recess 422L of base16, as aforesaid. rl`he material of blade 20 in the exemplary embodimentwas of Phosphor bronze, .7010" thick. vThis is to alord Va spring actionof body 80 of blade 20 for the purposes set forth. The lips 22, 22Aextending from body Silof blade 20 are for gripping the insulation board2.1 to the top of blade 20 as shown in Figure 2.

Y kprojection 81 from blade body80 recesses in the opening 82 ofinsulation vmember 21. Projection 8l prevents longitudinal displacementof the board 21 on blade 20, otherwise gripped by the opposed lips 22,22. The leg 42 has projecting lugs 83, 83 stamped therein to co-.actwith a corresponding'notch or groove in the v'ertical recess 42a of base1 6; whereby the blade 20 is held in operative position on base 16.

The body 80 of blade V20 is designed to be set at an angle (A) with thehorizontal base 16 of the order of 15; more or less, as desired. Lugs84, 84 extend from the back end of body 80 and rest upon top of the base16, and contribute to the spring action of blade 20. In the preferredembodiment, the overall dimensions of blade 20 is comparable to those ofthe top face of mounting base v16 upon which it operates. In a typicalcase, the length of leg 42 was on the order of one-'third inch.

The ready simplicity and assemblage of device 15 will now be apparent.lndu'ctance' loop 17 is designed to be inserted into mounting base 16 inrecess 57 thereof, and locked into position through its dependingintegral lugs 54, 55, 56. Capacitive blade 20 is similarly locked intobase 16 through leg 42 thereof, and its extending lug 83. Insulationplate 21 is fastened to blade 20 through lips 22, 22 and held inposition by llug 81.V The assembled ne tuning device 15` is mounted tochassis plate 75, through projecting hook 70, affording a rigid mountingof thev device. The fine tuning shaft 45, :ha-ving recess'46, operatesthe device 15 connected inthe oscillator 25 circuit. It is to beunderstood that the exemplary tuning device r15, illustrated in Figures1 to 10 herein, has been shown for illustrative purposes, and thatmodifications thereof for effecting the novel results herein, will nowbe :apparent to those skilled in the art, without departing from thebroad spirit and scope of the invention.

A modified form for a iine tuning mechanism within the scope of thepresent invention is illustrated in Figures 11 Yand 12 at 100. Referenceis made toFigure ll, where in a cylindrical insulation tube 101 isprovided with bilar windingsl102, 10,3, connected to an oscillatorcircuit 25 similar to that of Figures l and 3. Fine tuning device 100contains a coil, 102 in connection between terminal 6 31 of inductance30 and anode 27 of oscillator 25. The winding of coil 102 are spaced andaccommodates the other coil 103 between its windings, in the form of abilar arrangement.

Coil 103 is connected end to end at terminal 104 and in turn isconnected to lead 38 of oscillator 25. It is to be understood thatvariousl connections of the tine tuning device 100, as of device 15, arefeasible within the exemplary oscillator circuit 25 or in any otherelectronic oscillator used instead, without departing from the spirit orprinciples of the invention. The circuit connections shown herein aremerely for exemplary purposes. The coil103is yaccordingly capacitativelyrelated to the induct ance 102 for the purposes to be set forth.

A metallicvslug 105 is slidable within coil form 101 through a rod 106in the longitudinal backend-forth relationship shown by arrow c. Theposition of slug 105 can be varied fnlly within the extent of theinterio'rvof the windings 102, 103 as shown at 1052i. Material for slug105 is preferably brass but may be of aluminum or other suitablemetallic material. The movement of slug 105 to within bilar coils 102,103 by rod 106 causes an increase in the capacitance between these twowindings. Such movement of slug 105 within coil 102 also serves toreduce the inductance thereof effective in oscillator 25; The result isan equalization in the range of tine tuning of the device 100, in asimilar manner to that of device 15` hereinabove described..

Reference is made to Figure l2 which is a schematic representation ofline tuning -device in circuit with oscillator '25. The v4winding 102 isin series connection between inductance 30 of the oscillator and Atheanode 27 thereof. The winding 103, wound in the interstices of thespaced winding of coil 102, is connected end-toend at point 104, andserves effectively as a capacity plate, shown at 110, through coil 103.The turns of inductance 102 effectively form anoother capacity plate111, to coact with the capacity plate effective at 110. A capacity C1,vshown vin dotted, is accordingly effected between the bilar relatedwindings 102, 103 at the frequencies encountered in oscillator circuit25, herein. The brass slug in Figure l2 is movable between the effectivecapacity plates 110, 111 in the longitudinal relationship correspondingto arrow c. An intermediate position of the slug` 105 `between plates110, 111is shown at position 105e. The movement of the slug 105' to inybetween the effective condenser plates of windings 1 02, 103(corresponding to plates 110, 111) causes an increase in the capacitybetween the plates 110, 111. Such capacitance (C1) changes by movementsof slug 105 correspondingly shifts the frequency of oscillator 2S, asVwill now be understood by those skilled in the art.

AAs the 'frequency of oscillator 25 is increased, e. g., for the higherchannels in the V. H. F. range, the effective inductance 102 isdecreased at these higher frequencies due to the presence of the brassslug 10Sa therein (see also Figure 11). As will now be understood,reducing the inductance at 102, corresponding to variable L1, inconjunction with the increase in capacitance C1 as the brass slug is atthe fuller inside position 1058, provides for the higher frequencies anoverall lower capacitance effect for the frequency changes at theoscillator. The overall band for the V. H. F. channels has been found tobe provided, with device 100, a relatively linear effect with slug 105travel.

The frequency changes (shifts) provided over the overall twelve channelsin the V. l1'. F. band are substantially the same for each channelthroughout the band, using the invention device in the oscillator of atuner.

The mechanism 100 may be used as an oscillator trimnier as well. In suchapplication the slug 105 is moved to alposition in tube 101corresponding to the approximate frequency `setting for oscillator 25desired. Variation of such position, through external action on rod 106,effects trimming frequency shifts in oscillator 25.

essere 7 A further exemplary embodiment of the tine tuning device 15,corresponding to Figures 1 and 2, is illustrated in Figure 13. Thetuning unit 125 is basically constructed like device in that it has aninsulation base 126 with a recess 127 in which the at inductance loop123 is supported, and the capacitance blade 130 is angularly mountedthereon with its leg 131 projecting through recess 132 in base 126.

Loop 128 is secured to base 126 by clips 133, 134, 135. Circuitconnection to loop 126 is made torend projecting lip 136 and theopposite end 137 thereof. A projecting arm 138 of blade 130 extendsbeyond base 126, and electrically grounds blade 130 to metallic chassisor base 140 such as by soldering at opening 141.

Base 126 of device 125 is tiltably mounted on base 140, being adjustablewith respect to control cam 142. The adjustable mounting means for theline tuning device 125 comprises an adjusting screw 145 projectingthrough chassis 140 to mechanically co-act at its end portion 146 with aportion 147 of base 126, and a retaining spring 150 engaging leg 132 atnotched end 151 thereof and abutting chassis base 140. Spring 150 isarcuate and of flat material. As seen in Figures 13 and 14, one edge 152of rectangular retaining spring 150 abuts a knock-out lip 153 of chassis140. The edge of spring 150 opposite edge 150 comprises two legs 154,154 pressed in spring fashion against chassis 140.

ln operation, fine tuning device 125 is controlled in its frequencyshifting or changing function by the rotation of cam shaft 142 in eitherdirection a, to move blade 130 angularly withrespect to normallystationary inductance loop 128 along b as described in connection withFigures 1 and 2. Y

In accordance with the features of tine tuning device 125, the furtheradjustment thereon by adjusting screw 145 controls the actual electiverange of displacement between loop 128 and blade 130 through control142. Rotation of screw 145 causes base 126 to move to or from chassis140 along the direction per arrow c. A displacement to the dottedposition of the base at 126' and the inductance loop at 123 results frommotivation of screw end 146 upwardly. Since the positions of movement ofcapacitive blade 130 are defined by the fixed cam shaft 142, a newposition as 128 of loop 12S, closer to blade 130 at all its movementsresults in a greater maximum capacitance action due to a closer angularposition of blade 130 to loop 128, as will now be understood.

Thus a greater or lesser overall effect in the frequency control bydevice 125, in an oscillator circuit such as oscillator of Figure l, isadjusted as desired or required by setting adjusting screw 145. Screw145 is locked in its set position by lock-nut 155. Retaining spring 150serves to hold device 145 stably on chassis 140 in all adjustedpositions.

In a physical embodiment of device 145 as used in a V. H. F. tuneroscillator circuit, the minimum spacing between the outside end 156 ofblade 130 and the opposite end 157 of base 126 was 0.050 when the base126 was in its lowest position in Figure 13 as shown in solid lines.Adjustment by adjusting screw 145 of base 126 upwardly to the maximumextent, such as shown at dotted base-top position 157', caused thelowest position of blade tip 157 to contact base 126 at 157', and effectthe maximum capacitive correlation between blade 130 and loop 128.However, this is given by example and other parameter values may be usedin practice.

Figures 15 and 16 illustrate an exemplary tuner 160 contructionembodying the fine tuning device 125 of Figure 13. Tuner 160 comprisesmain tuning shaft 161 (for V. H. F.) Vshown in dotted lines internallyof the tuner, and having a flattened end 162 for'a knob. A further shaft163 is concentric about shaft 161 and may be used for U. H. F. frequencycontrol, or omitted in a V. H. F.-only tuner. The extending flattenedend 164 of shaft 163 is for a knob (not shown). The outer tubular shaft165 is the line tuningshaft, rotatably secured on inner shaft 163 byVclip 166, and having flattened end 167 for a knob. The shaft 16Scontrols the fine tuning of the tuner 160, usually at itsoscillatorvcircuit by actuating the device in circuit therewith andmounted on the chassis 168 of the tuner 160.

The line tuning device 125 is basically shielded within tuner 160 andhas its adjustingscrew 145and locknut projecting; as does retainingspring 150 securing lip 151. Screw-nut 145, 155 (when set) and spring150 hold device 125 securely in position whereby its spring blade 130co-acts with and is movable by cam shaft 142. Alsopsee Figure 13.

Rotation of cam shaft 142 is effected by ne tuning shaft 165 through camlever 170 operating in spiral cam unit 171 at one end and on pin 172 ofdisc 173 at the other end. 'Cam shaft 142 is suitably mounted in tunerand is rotatable by action of cam lever 170 on pin 172 on the disc 173secured to shaft 142.

Cam lever 170 has two fingers 174, 175 with corresponding projections176, 177 arranged to engage a spiral slot 178 n plate 180 of mechanism171. A springnger 182 of lever 170 presses against plate 181 spacedlymounted opposite plate 180, and holds lever 170 in operative positionbetween plates 180, 181. Plate 131 is secured to tuning shaft and inturn rotates plate 180 to displace cam lever through the projections176, 177V thereof riding in spiral slot 178.

Rotation in either direction, arrow a causes radial displacement b oflever 170 to in turn result in corresponding rotational displacement ofdisc 173 per arrow c in Figure 15. The line tuning by device 125 fortuner 160 is thus accomplished by operation of fine tune shaft 165, aswill now be understood by those skilled in the art. l It is to beunderstood that the invention described herein is subject to furthervariation and modification without departing from its function andoperation, all within the broadest spirit and scope of the invention asdefined in the appended claims.

l. A fine tuning device of the character described for an oscillatortunable over a wide frequency range comprising an inductive memberconstructed in a plane and connectable in the oscillator circuit, a bodyof insulation material carrying the plane inductive member parallel to afiat surface thereof, a blade of spring material supported at one end insaid body at an angle above said member and surface, said blade beingcapacitatively related to said inductive member and angularlydisplaceable with respect thereto about said one end through biasedjuxtapositioning of its other end, against a cammed control memberwhereby the oscillator frequency isV varied by said control member. Y l

2. A line tuning device as claimed in claim 1, wherein said planeinductive member is in the form of a single loop with integral clipmeans projecting therefrom for coacting with corresponding areas of saidbody to hold said loop firmly in position.

3. A ne tuning device as claimed in claim l, in which said blade has anintegral prong extending from its said one end through said body and outat the base thereof opposite said surface forsecuring the device to achassis portion.

4. A tine tuning device as claimed in claim 2, in which i (References onfollowing page)V References fired in the le of this patent UNITED STATESPATENTS Van Billiard Feb. 8, 1944 10 Vladimir July 12, 1949 BeusmanSept. 12, 1950 Torre June 5, 1951 Snyder June 24, 1952 Osborn Nov. 2,1954 Julian June 11, 1957

